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AR-15 gunsmithing for the novice: installing a barrel: part 1.

Putting together an AR is easy, right? Well, it is if you have the right tools and techniques. Matthews provides a few pointers.

One of the most popular AR-15 customizing jobs is replacing the original barrel. There are hundreds of different barrels from which to choose. AR-15 barrels are available in different lengths, steel types, rifling twists, shapes and contours, and at all price points.

Whether it's target shooting, hunting, plinking or self-defense, there is a barrel made specifically for that application. AR barrels can be easily changed by the hobbyist with a few tools and the knowledge needed to do it correctly.

Unlike bolt-action firearms that require expensive tools and advanced gunsmithing skills to set headspace, the AR-15 barrel can be changed by those with minimal tools and skills.

The excellent design and the tolerances that can be held with modern firearms production equipment mean AR15 barrels and bolts can be "pre-headspaced." AR-15 bolts and barrels can be made so that all brands of bolts will mate correctly with all brands of barrels, or at least they do on paper.

In fact, there is no easy way to change the headspace setting on an AR-15 beyond substituting parts made to slightly different tolerance levels. Even though all AR-15 bolts and barrels are supposed to fit together correctly, you should still check them for headspace to verify that they have not got defective parts.

I chose three of the most common AR barrels and installed them on identical receivers. The first barrel was a 20-inch chrome-lined A2 format barrel such as found on GI rifles.

It features a smaller diameter t under the handguard and a larger diameter in front of the front sight/ i gas block. The small diameter un, der the handguard makes it a very light barrel by today's standards.

This lightness however comes at a price. The thin profile means it is not very stiff, and the point of impact can be affected by outside forces bearing on the barrel. Point of impact can change a couple inches if you are pushing hard against one side of the barrel when shooting.

This is one of the reasons why people replace this barrel with a heavier version. I picked up this particular barrel used at a gun show for $ 15. The exterior was extremely worn, but the bore looked pretty good.

It was missing the barrel extension (that incorporates the locking lugs), the front sight/gas block, and flash suppressor. I figured if I invested about $30 worth of parts and a couple hours of labor, I could end up with an inexpensive barrel for some future project.

This is a perfect example of how hobby gunsmithing can save you a lot of bucks. A new chrome-lined GI format barrel would cost about $200. I really didn't have high expectations for this barrel, but I couldn't pass up a bargain.

The next barrel is what is generically referred to as an H-BAR barrel, which is just slang for heavy barrel. This brand new 20-inch barrel featured a very thick diameter (just under an inch) under the handguard and a diameter of just under 3/4" forward of the front sight.

The larger diameter makes the barrel stiffer than a GI format barrel and this usually results in better accuracy. The example featured here was made by Stag Arms, which has a very good reputation for quality AR-15 parts.

This barrel is what is called a chrome-moly barrel. This is not the same as a chrome bore barrel. Chromemoly refers to the type of steel used to make the barrel, not the chrome plating that is featured on a chrome bore barrel.

Chrome plating of the bore is usually found on military specification barrels since it helps resist corrosion and may increase barrel life under hard military usage. Chrome bore barrels offer little benefit on sporting arms and add significantly to the cost. This barrel is priced just under $200.

The last barrel was also a 20-inch heavy barrel but not your average heavy barrel. It was a match-grade target barrel made to exacting standards. It is made from stainless steel and comes with its own bolt mated to the barrel for maximum accuracy potential.

It is chambered in what is called .223 Wylde. This is a specialty chamber that is a combination of 5.56 NATO and .223 Rem. chambers that allows you to use either type of ammo.

While many consider 5.56 NATO and .223 Rem. ammo and chambers to be interchangeable, there are actually slight differences between them, and you should not mix the cartridges and chambers.

If your gun is chambered for 5.56 NATO, you should use 5.56 ammo, if it is chambered for .223 Rem. you should use .223 Rem. ammo. This is a hotly debated issue in the gun hobby and there are many that say the rounds are completely interchangeable.

While it is generally agreed that it is acceptable to shoot .223 Rem. ammo in 5.56 NATO-chambered guns the issue of contention is if it is acceptable to shoot 5.56 ammo in .223 Rem. guns. I prefer to err on the side of caution but you can research this issue more in-depth yourself and make up your own mind.

The match grade barrel featured here was made by Shilen and obtained from Brownells (part #787-000-034, priced at $440). This type of match barrel is not cheap, but quality costs money.

To change AR-15 barrels, you do need a couple special tools. While I improvise as many tools as possible to save money, there are some cases where you just have to bite the bullet and buy the correct tool.

Improvising tools can save a lot, but the idea should only be taken so far. Under no circumstances should you ever try to use a pipe wrench on a barrel nut nor should you ever simply clamp an upper receiver into a vise without a special holding fixture.

A pipe wrench will ruin a barrel nut even if it does tighten the nut, and a receiver clamped in a vise will likely bend, no matter how many rags you wrap around it.

AR-15 gunsmithing tools can be found from many sources but I get most of my gunsmithing supplies from Brownells. They offer their products through their website ( or through their massive print catalog.

Besides offering products for sale, Brownells is also a source of free gunsmithing information on how to use the products they sell. Even before I started writing, Brownells helped me learn gunsmithing with their free technical information.

The first thing you will need is a sturdy bench vise (5 to 6-inch jaws) to hold your parts or tools. You may need to exert over 75 foot-pounds of force to remove some stubborn barrel nuts, so you need a stout vise that is solidly secured to a heavy-duty workbench.

Good vises are available at most hardware or tool stores. While I won't specify any particular brand or source but I will say that you should buy the largest vise you can afford. Very seldom will you find yourself saying that you needed a smaller vise but you will often find you need a larger one if you buy one too small.

The barrels of AR rifles are secured with an odd shaped nut that requires a special wrench. There are several styles of barrel nuts on the market since some specialty handguards require their own unique barrel nut.

The most common type is the GI style barrel nut that is found on stock military format guns. This looks like a thin collar with bumps and notches all around the exterior.

The second most common type is the style that is used on many free-floating handguards. This type most often looks like a thick round collar than has a series of holes drilled just inside the outer edge all the way around the periphery.

Some free float hand guard barrel nuts require their )wn special wrenches but the types featured here take general-purpose barrel nut wrenches.

I have two types and either will work fine. The first is generally referred to as GI combination tool. This is a multi-purpose tool that is made from a thick plate of steel. It has several notches and cut outs to serve several purposes when working on AR rifles.

To engage barrel nuts, it features two or three pegs that engage the notches on a GI type barrel nut. The pegs will also engage the holes on many free float handguard barrel nuts such as the ones featured in this article. The tool is only about 4 inches long, so for leverage you must attach it to a 1/2" ratchet or breaker bar.

This tool is available from many AR parts sellers as veil as Brownells (#080-216-015, $35). The other tool is also a combination tool but it is shaped differently. It is larger and does not require the use of a ratchet or breaker bar. There are many variations of this tool available from a lot of AR parts suppliers. Naturally I got mine from Brownells. It is a DPMS brand (#231-000-007) and is priced at $34.50.

Since the barrel nut may require a lot of torque to loosen and 35-65 foot-pounds of torque to tighten, you must securely hold the receiver or barrel during installation.

There are several ways to do this. I have four ways of doing this even though I only use three of the ways most often.

The first improvised method is to clamp the barrel into a heavy duty vise to hold it. To protect the barrel, you need to place hardwood boards between the vise jaws and barrel. The barrel will be very tight in the vise, so you need to use hardwood and also observe grain direction to prevent splitting the blocks when tightened.

The next method is to use specialty vise jaws to protect the barrel. Brownells offers two different types. One style is made completely from aluminum (#795-015-100, $28) and the other one (#852-015-000, $63) features polyurethane liners in the aluminum jaws to eliminate any chance of damaging the barrel's finish.

Rather than gripping the barrel for nut tightening you can grip the upper receiver instead. To do this, you need a fixture. Never clamp a receiver in a vise without some type of fixture, otherwise you run the risk of damaging it.

Brownells offers a set of plastic hinged blocks (#080000-661, $60) that surround the receiver. These blocks evenly grip the receiver and protect it from the vise jaws.

There is one last method for holding the parts which I have tools for but have never used. Both Brownells and Geissele make a tool that engages the locking lugs in the rear of the barrel to allow tightening of the barrel nut.

Brownells calls theirs a barrel torque tool (#080-000637, $38). The similar Geissele version (#100-011-315, $99) is also offered by Brownells. Both work the same but the method to hold the tool varies between the two types.

These tools insert through the rear of the upper receiver and the notches in the front insert into the rear of the AR barrel.

Since the tools engage the rear of the barrel, there is no stress placed on the receiver or forward portion of the barrel. Someone gave me these tools awhile back and I have never used them simply because I am used to using the other methods. People who do use them do really seem to like them according to website reviews.

The first barrel I installed for this article was my greatly used 20-inch GI format lightweight barrel. I clamped it into my vise with wood blocks between the barrel and vise jaws.

You will have to tighten the vise very tight to prevent the barrel from turning under torque. I have found that wrapping the barrel with a sheet of fine sandpaper greatly increases grip of the wood jaws, although it can scuff the barrel a little.

When clamping the barrel in the vise, place the breech as close to the jaws as possible. Leave only enough room to use your barrel wrench. Be sure to install your delta ring assembly on the barrel nut before installing the barrel into the receiver.

Once the barrel was solidly clamped in the vise, I slipped a flattop receiver over the barrel extension.

Before screwing the barrel nut to the receiver place a little grease on the threads to ease tightening and to prevent galling the threads. Screw the nut on hand tight.

I used the DPMS combination tool to tighten the barrel nut. It has two pegs that can engage the notches on the barrel nut, as well as section that has an impression of the barrel nut notches formed in the tool. Either part can be used.

The spring tension of the delta ring assembly is always trying to push the tool out of engagement, so you need to apply constant pressure to keep it engaged.

If you let it slip, you run the risk of damaging the tool or nut.

The torque needed to tighten a barrel nut varies widely, from 35-65 foot-pounds. This allows the nut notches to align with the gas tube hole in the front of the receiver.

Unfortunately, tightening to the preliminary torque of 35 foot-pounds seldom aligns the notches. It may require 65-70 foot-pounds to get the notches aligned. Any more torque than this may strip the soft aluminum threads.

It is very difficult to determine correct alignment by eye; you need a simple alignment checking tool. While you can buy tools for this job, I take a bolt carrier and remove the bolt assembly.

I insert a straight #14 drill (.182") into the carrier key.

The carrier is inserted into the receiver with the drill bit passing through the gas tube hole, notches in the delta assembly and finally through the notches in the barrel nut.

Unfortunately, even with the extra tightening my notches were still off. I have installed more than 75 AR barrels and the notches only align with the recommended torque about half the time. So what does one do to get the parts aligned?

We'll get to that next time.

Caption: AR-15 barrels originally featured light weight thin profiles. Today, many hobbyists prefer heavy profile barrels. Heavier barrels many times offer better accuracy.

Caption: The smaller barrel nut is an original GI type while the larger one is used on today's free float hand guard systems that include the barrel nut.

Caption: To engage the barrel nut, you will need a special wrench. The small tool is a GI type combination tool. The larger Tool is a DPMS combination tool, offering more leverage.

Caption: On the GI type combination tool, pegs engage the notches on a standard GI format barrel nut. Other features on the tool engage various other AR parts.

Caption: The DPMS combination tool features an impression of a standard barrel nut formed in the tool. It also has pegs on the opposite side like the GI tool. Both work.

Caption: The increased rigidity of heavy barrels tends to make them more accurate, though barrel quality counts, too. There's an obvious weight penalty with heavy barrels.

Caption: Holding the barrel securely while working is vital. This may be done with receiver blocks (top), barrel vise jaws (center), or a barrel lug engagement tool (bottom).

Caption: Receiver blocks surround the receiver and evenly grip the receiver when it is placed in a vise. The T-shaped part helps prevent crushing when the vise is tightened.

Caption: The Geissele Reaction Rod and Brownells Barrel Torque Tool engage the locking lugs in the rear of the barrel, taking all turning stress off the receiver.

Caption: >These Polyurethane-lined aluminum vise jaw blocks securely grip the barrel during installation, yet protect its finish. They fit two barrel diameters.

Caption: A #14 (.182") drill bit inserted into the bolt carrier key can be used to make an improvised barrel nut alignment tool. If it passes through, the nut is aligned.

Caption: As is often the case, the specified barrel nut torque does not allow for correct notch alignment. Hand fitting is now needed to get the correct alignment.
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Author:Matthews, Steven
Publication:Firearms News
Date:May 20, 2017
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